We use sine and cosine functions of different frequencies just as “positional encoding” [1]}:
\(FE_{\left( time, 2i \right)} = sin\left( time / 10000^{2i/d_{model}} \right)\) 
\(FE_{\left( time, 2i+1 \right)} = cos\left( time / 10000^{2i/d_{model}} \right)\) 
